Any other local public entity may contract with the county to employ the services of the county hearing officer. The duties and responsibilities of the hearing officer described in Sections 27721 and 27722 shall be set forth in the contract. Reimbursement to the county for the services of a county hearing officer shall be made as provided in the contract. If no provision for reimbursement is contained in the contract, reimbursement shall be made on a pro rata basis of actual cost to the county in providing the service including salaries, benefits, overhead, and any travel expense.